State detecting devices for assessing the activity level of drivers are disclosed, for example, in Patent Documents 1 and 2 and a Non-Patent Document 1.
The state detecting device disclosed in the Patent Document 1 calculates the standard deviation of the movement of the vehicle in the direction perpendicular to the travelling direction. This state detecting device detects the vigilance level of the driver based on the results of comparing the calculated maximum and minimum standard deviations with thresholds.
The state detecting device disclosed in the Patent Document 2 continuously detects the direction of sight line of the driver for a given period of time. This state detecting device creates sight line profile information presenting the profile of the detected sight line direction. The state detecting device determines whether the driver is driving inattentively based on the direction of sight line presented by the created sight line profile information.
The state detecting device disclosed in the Non-Patent Document 1 detects the heart rate of the driver fluctuating according to his/her mental stress as a characteristic quantity. This state detecting device detects the driving stress of the driver by matching of the characteristic quantity using AdaBoost.